1. Field of the Invention
This invention relates generally to an X-ray diagnostic system, and is concerned in particular with a diagnostic system with an X-ray camera supported by an arm, which is provided with a system for compensating offsets in an X-ray irradiated field.
2. Description of the Prior Art
A conventional X-ray diagnostic system, such as a system for diagnosing circulatory organs includes an arm which supports an X-ray source such as an X-ray tube at one end and an X-ray camera opposing the X-ray tube at the other end. The arm is usually formed in a C-shape or an .OMEGA.-shape in order to maintain sufficient inner space to permit the X-ray tube and X-ray camera to be set at various positions around the patient.
However, a large arm bends from the weight of an X-ray tube and its accessories, and causes offsets in the X-ray irradiated field.
As a result of the offsets, not only the required part radiographed is, but also parts of the patient are irradiated inadvertently when an autocollimator is used. This problem become more serious when larger the X-ray diagnostic systems are used.
Conventional systems solve the above-mentioned problems in the following manner;
(i) Utilization of an arm with more rigid members to reduce the amount of bending.
(ii) Changing the location and angle at which heavy devices such as an X-ray tube, an X-ray diaphragm device or an image intensifier are attached so that the amount of bending is decreased.
However, it is not always possible to utilize large and rigid arms, because these require a lot of space and as a result insufficient space is provided for operating the devices. In the future, X-ray diaphragm devices and image intensifiers are expected to become larger and heavier, thus exacerbating the problem will be more serious. It is very difficult to eliminate the offsets of the X-ray irradiated field for every position and angle of the arm simply by changing the locations and angles at which the image intensifier or the X-ray tube are attached.
Therefore, the use of a conventional X-ray diagnostic system with a large arm leads to substantial offsets in the irradiated field. This makes it difficult to irradiate at an exact location and to prevent unwanted irradiation of the patient.